1. Field of the Invention
The invention relates to an open-end spinning apparatus having a spinning rotor revolving in a rotor housing and a spinning insert being disposed coaxially to the rotor axis and being supported rotatably with respect to the spinning rotor.
German Published, Non-Prosecuted Application DE-OS 25 52 955 discloses an open-end spinning apparatus that has both a spinning rotor and a spinning insert supported rotatably inside the spinning rotor. The spinning rotor has a rotor shaft, constructed as a hollow shaft, that revolves on a support plate bearing. Inside the hollow shaft, a drive and bearing shaft of the spinning insert is supported in roller bearings.
The drive of the spinning rotor and the spinning insert is effected through a common tangential belt. In order to obtain the required differences in rotary speed between the spinning rotor and spinning insert in such rotor spinning apparatuses, drive wharves of the two shafts are dimensioned differently.
Open-end rotor spinning apparatuses conceived in that way have not proven themselves in practice.
A further development of the above-mentioned open-end rotor spinning apparatus is the subject of German Published, Non-Prosecuted Application DE 42 25 087 A1. In that known spinning apparatus as well, the spinning rotor with its rotor shaft constructed as a hollow shaft rests on a support disk bearing. Moreover, as described above, roller bearings are disposed inside the hollow shaft and receive the bearing shaft of a spinning insert. The bearing shaft of the spinning insert protrudes beyond the hollow shaft of the spinning rotor in the rear region and is supported through an axial bearing. The drive of the spinning rotor and of the spinning insert are each effected through a separate tangential belt. Since the circumferential speed of the spinning insert must be higher relative to the circumferential speed of the rotor groove by the amount of the yarn draw-off speed, it proves to be very complicated and expensive to control that kind of double drive, in which the speed ratios also change depending on the draw-off speed of the yarn.
It has also already been proposed (in German Published, Non-Prosecuted Application DE 33 02 676 A1) that a spinning insert rotatably supported in the spinning rotor be driven directly by the yarn. Despite the high rotor rpm, that is possible because the relative speed between the spinning rotor and the spinning insert is relatively low. However, in such an apparatus, problems arise in piecing.
Since the bearing of the spinning insert in the rotor must be constructed to run quite smoothly, so as not to put excess strain on the yarn as it entrains the spinning insert, the spinning insert remains far behind upon acceleration of the rotor and must be accelerated by the newly pieced yarn. In that process the yarn is often overloaded, and therefore the piecer fails.